The invention relates to the field of intravascular catheters, and particularly to a catheter suitable for angioplasty and/or stent deployment, and the like.
In percutaneous transluminal coronary angioplasty (PTCA) procedures a guiding catheter is advanced in the patient""s vasculature until the distal tip of the guiding catheter is seated in the ostium of a desired coronary artery. A guidewire is first advanced out of the distal end of the guiding catheter into the patient""s coronary artery until the distal end of the guidewire crosses a lesion to be dilated. A dilatation catheter, having an inflatable balloon on the distal portion thereof, is advanced into the patient""s coronary anatomy over the previously introduced guidewire until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with inflation fluid one or more times to a predetermined size at relatively high pressures so that the stenosis is compressed against the arterial wall and the wall expanded to open up the vascular passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter and the guidewire can be removed therefrom.
In such angioplasty procedures, there may be restenosis of the artery, i.e. reformation of the arterial blockage, which necessitates either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate of angioplasty alone and to strengthen the dilated area, physicians now normally implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel or to maintain its patency. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded within the patient""s artery to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter and the stent left in place within the artery at the site of the dilated lesion. See for example, U.S. Pat. No. 5,507,768 (Lau et al.) and U.S. Pat. No. 5,458,615 (Klemm et al.), which are incorporated herein by reference. Thus, stents are used to keep open a stenosed vessel, and strengthen the dilated area by remaining inside the vessel. Instead of first using one catheter to dilate the body lumen and a second catheter to deploy the stent after the dilatation, the stent may be mounted on a balloon catheter and deployed at the same time the balloon is inflated to dilate the stenotic region.
Conventional balloon catheters for intravascular procedures, such as angioplasty and stent delivery, frequently have relatively stiff proximal shaft sections to facilitate advancement of the catheter within the patient""s body lumen and a relatively flexible distal shaft sections to facilitate passage through tortuous anatomy such as distal coronary and neurological arteries without damage to the luminal wall. Typically, there is an intermediate shaft section or junction between the relatively stiff proximal shaft section and the relatively flexible distal shaft section which provides a transition between the proximal shaft section and less flexible than the distal shaft section.
A variety of intermediate shaft or junction designs have been utilized to provide a relatively smooth transition between the stiff proximal shaft section and the flexible distal shaft section. However, it has been difficult to develop a catheter design with an intermediate catheter shaft junction which provides a smooth transition and improved flexibility and which is also leak free when utilizing high pressure inflation fluid to inflate the balloon on the distal shaft section of the catheter for dilatation or stent deployment. Furthermore, they tend to kink when bent, into tight radius curves. The present invention satisfies these and other needs.
The invention is generally directed to an intraluminal catheter system with an improved transition between a proximal shaft portion and a more flexible distal shaft portion. The improvement provides enhanced flexibility and kink-resistance, thus, facilitating advancement through tortuous anatomy. The present catheters may be used for either or both angioplasty and stent deployment.
The improved flexibility allows the device to turn tight corners along the vasculature without applying large forces against the wall of the vessels, thus minimizing the surface friction between the catheter and the vessel. This allows more distal access. This optimization of flexibility may aggravate the kinking dynamic, as for example, bending stiffness discontinuities can be more pronounced as some softer catheter members are more likely to kink than stiffer members. Kinking of the catheter is also a common constraint to distal access. The kink creates a hinge point in the catheter so that the catheter can no longer navigate tight radius turns in the vasculature. Kinks often occur at the interface of two regions along the device having substantially different bending stiffness (i.e., have a discontinuity in the bending stiffness).
The kink resistance has been achieved by minimizing the differential in bending stiffness at the troublesome regions. The present invention includes various embodiments for minimizing the bending stiffness differential as well as increasing the overall flexibility of the catheter.
The catheter of the invention has an elongated proximal shaft section which transitions to a more flexible distal shaft section through an improved transition disposed between the proximal and distal shaft sections. An inflation lumen extends within the catheter shaft to a location spaced proximal to the distal end. An inner tubular member having a guidewire receiving lumen extends within at least the distal shaft section of the catheter. The proximal shaft section has proximal and distal ends and a portion of the inflation lumen extending therein. The distal tip of the proximal shaft section is preferably tapered distally to smaller transverse dimension. The distal shaft section has the inner tubular member extending within the distal shaft section to the port in the distal end thereof, and at least part of the inflation lumen extending within the distal shaft section to a location proximal to the distal end of the distal shaft section. An inflatable member such as a balloon is preferably provided on the distal shaft section which has an interior in fluid communication with the inflation lumen.
The transition includes a proximal portion of the distal shaft section and a distal portion of the proximal shaft section. At least a portion of the transition further includes, a tubular support member with an inner lumen extending therein, secured at a proximal end to the distal end of the proximal shaft section. Preferably, the tubular support member includes, a composite tubular member, which in turn, can include a tubular metallic member. The tubular metallic member includes at least one layer of metallic strand, in forms such as a metallic wound (or coil) or braid. Preferably, the composite tubular member includes polymeric inner and outer layers disposed on either side of the tubular metallic member.
In a preferred embodiment, the distal portion of the tubular support member further includes a tubular polymeric member having proximal and distal ends, with the proximal end extending proximal the distal end of the composite tubular member.
An intermediate portion of the tubular support member forms a junction 202, with the outer tubular member and the inner tubular member, the junction having a proximal end substantially being at the same longitudinal point as the outer tubular member aperture where the inner tubular member enters the outer tubular member, and is distally spaced apart from a distal end of the tubular support member. The junction may be formed by suitable adhesives, or mechanically connected by a suitable fastener or secured by a variety of other suitable means. The junction, preferably, is fusion bonded.